More than 700,000 total knee arthroplasty surgeries are performed annually to alleviate pain and disability associated with osteoarthritis; a chronic, degenerative condition present in 43% of Veterans using VA services. Although total knee arthroplasty intervention improves pain and self-reported physical function, objective physical activity remains low and nearly unchanged from pre-surgery levels up to one year after rehabilitation. These data suggest that current conventional rehabilitation, primarily directed towards acute post-operative impairment, does not address the key-underlying problem of persistent physical activity behaviors after total knee arthroplasty. The negative health consequences of low physical activity are well documented. Therefore, the primary aim of this randomized controlled trial is to assess the efficacy of physical activity behavior-change telerehabilitation as an adjunct to contemporary rehabilitation for increasing physical activity behavior following total knee arthroplasty. The novel, low-cost intervention incorporates evidence-based behavior-change methods and telerehabilitation technology. Outcomes will be assessed immediately before total knee arthroplasty, at rehabilitation midpoint, end of rehabilitation (primary end point), and 24 weeks after rehabilitation. The primary outcome will be accelerometer-assessed average daily step count. Secondary outcomes include: average daily time spent in standing and walking activity, self-reported physical activity (Life Space Assessment), performance-based physical function (30-Second Chair-Stand Test, Timed Up-and-Go, Six-Minute Walk Test), self-reported physical function (Western Ontario and McMaster Universities Osteoarthritis Index and Veterans 12-Item Health Survey), healthcare utilization and secondary health problems. The distinct and unique rehabilitation paradigm used in this study addresses the problem of chronic poor physical activity following total knee arthroplasty. The proposed intervention also adds value to current VA telerehabilitation technology by improving rehabilitation accessibility. The products of this trial will advance rehabilitation knowledge and provide necessary evidence for the clinical implementation of physical activity behavior-change telerehabilitation for the large population of Veterans recovering from total knee arthroplasty.